Stir chocolate in top of double boiler set over simmering water until melted and smooth. Drizzle melted chocolate over top of tartlets. Chill until chocolate is set, about 30 minutes. DO AHEAD Mini tartlets can be made 1 day ahead. Keep refrigerated. Let tartlets stand at room temperature 1 hour before serving.

Freezing the tartlet crusts before baking reduces buckling and helps them hold their shape while they bake.